1. Field of the Invention
The invention relates to the field of wavelength and polarization tunable photonic crystal (PC) lasers and methods of switching the same.
2. Description of the Prior Art
Optics and fluidics have been historically integrated within systems that combine separate light sources, fluidic reservoirs and filters. Integration on a sub-millimeter scale has resulted in spectroscopic tools and liquid crystal (LC) displays. With the advent of photonic crystals (PCS) it has recently become possible to further integrate sources, filters and fluidic reservoirs and to define monolithic micrometer sized “opto-fluidic” devices”. With their intrinsically porous nature and ability to confine and manipulate optical fields, photonic crystals are ideally suited for nanoscale opto-fluidic integration. This miniaturization enables a much more efficient interaction between the optical field and the injected fluids and is leading to the emergence of a new class of functional opto-fluidic devices in which the optical functionality is controlled through the introduction of liquids.
Previous efforts in tuning photonic crystal laser emission have included tuning the emission by lithographically controlling the cavity size, infiltrating the photonic crystal with liquids of different refractive indices, and also by electrostatically rotating infiltrated liquid crystal. All three methods tune emission by changing the effective cavity optical path length.
The major drawback of lithographic tuning is that it is static, because a given fabricated laser has a set emission wavelength. Tuning is achieved by fabricating multiple lasers with different cavity geometries.
The second method, namely infiltrating a photonic crystal laser with liquids featuring different refractive indices, can yield large tuning ranges but the tuning of the laser is a tedious process involving extraction of the infiltrated liquid and replacing it with another possessing a different refractive index.
The third method of tuning, namely via rotation of infiltrated liquid crystal, is limited by the relatively small effective cavity optical path length change achieved by rotating liquid crystal. Due to screening by the semiconducting slab and strong surface anchoring effects within the holes of the photonic crystal, the liquid crystal orientation can only be effectively controlled in the top cladding layer, thus greatly limiting the achievable tuning.
What is needed is an optically tunable laser and a method of tuning a laser which would be adaptable to functional opto-fluidic devices in which the optical functionality is controlled through the introduction of liquids.